New circular method enhances the reclamation of Maurliden
Ever since the mine in Maurliden closed in 2019, we at Boliden have been working on reclamation to restore and future-proof the area. In the near future, we will move to an entirely new method for backfilling the open pits, using paste produced from recycled tailings sand.
“This is a solution that both improves water quality and creates a more circular flow of materials. The goal is for the land that mining operations have borrowed in Maurliden to be returned in the best possible condition,” says Johan Nilimaa, Lead Project Manager for Boliden’s tailings sand recycling project.
Our mine in Maurliden began operations in 2000, and for almost two decades ore containing zinc, copper, lead, silver and gold, among other metals, was mined there. Since production was closed as planned in 2019, our focus has been on the reclamation work that will future-proof the area and sustainably restore the site’s natural values.
“We want to leave behind an area that can be used in a natural way by the people who spend time here. That includes everyone from berry pickers to people involved in reindeer husbandry in the area, and we maintain a dialogue with those affected to ensure that the work is carried out in a way that allows them to spend time in nature,” says Johan Nilimaa.
A central part of the reclamation of Maurliden is to backfill and cover the open pits, in order to reduce the risk of acidic, metal-bearing water affecting soil, groundwater and nearby watercourses. The method previously used involved backfilling the open pits with waste rock and adding lime, but studies have shown that the method does not meet our environmental requirements related to water quality and impacts on the surrounding area.
New method using paste from recycled tailings sand
For several years, Boliden has been running a project to recycle tailings sand, with the aim of creating more circular mining operations and extending the life of the Boliden Area. Tailings sand is a residual product from the concentration process which, until now, has been pumped out and stored at the tailings facility in Hötjärn. However, as the remaining life of the facility only extends to 2029, we needed to find another method for managing the tailings sand. The solution was to recycle the sand to produce a paste, consisting of a mix of tailings sand and binder, which can be used for backfilling the underground mines in Renström and Kankberg and for the reclamation of the two closed open pits in Maurliden.
A tailings sand recycling facility, which will dewater the sand, is being built at the concentrator in Boliden. Once the sand is dry, it will be transported on return trips by ore trucks to the three mines, where newly built mixing stations will produce a paste that provides a more stable backfill and reduces contact between oxygen, water and reactive rock material when used in reclamation.
“Boliden is the first company in Sweden to use this type of paste for reclamation, and we have a strong belief in the method. There are also a number of reference projects in other parts of the world that we can rely on. The mixing station in Maurliden is to be ready for operation before the end of the year, and we expect to scale up production in early 2027,” says Johan Nilimaa.
Waste rock is moved to future-proof the surroundings
Another challenge in the reclamation of Maurliden is the waste rock pile located within the area. At present, it has no basal liner, which can lead to leaching and cause acidic, metal-bearing water to leak into the surroundings. The waste rock pile will therefore be moved to another location within the area and provided with a basal liner and a sealing layer of bentonite-treated till. The result will be, in practice, a sealed encapsulation that prevents water and oxygen from reaching the material.
“Moving the waste rock pile will continue until 2032 and is technically challenging, not least because the sealing layer has to function all the way until the next ice age. But we have robust monitoring programmes in place to ensure that the sealing layer meets the requirements,” says Johan Nilimaa.
Experts from all over the world
Reclamation of closed mines is a fundamental part of Boliden’s responsibility as a mining company and a prerequisite for being allowed to operate. Even before a mine begins operations, there must be a plan for how the area will be restored and secured once operations end. Johan Nilimaa emphasises that Boliden takes its responsibility very seriously and is an industry role model in areas including reclamation:
“At Boliden, we have the ambition to be the world’s most sustainable metals producer, and those are truly not just empty words. Enormous resources are being invested in restoring natural values, and I am proud to work for a company that takes responsibility at every stage and thinks so far ahead. Boliden is also good at recruiting people with the right expertise and has brought together experts from all over the world who are working together to find the best methods for reclamation.”